Complete Commentary on the Whole Bible, by Matthew Henry, at sacred-texts.com
(Ch2 21:1-11) The wicked reign of Jehoram.
(Ch2 21:12-20) Jehoram's miserable end.
2 Chronicles 21:1
Jehoram hated his brethren, and slew them, for the same reason that Cain hated Abel, and slew him, because their piety condemned his impiety. In the mystery of Providence such men sometimes prosper for a time; but the Lord has righteous purposes in permitting such events, part of which may now be made out, and the rest will be seen hereafter.
2 Chronicles 21:12
A warning from God was sent to Jehoram. The Spirit of prophecy might direct Elijah to prepare this writing in the foresight of Jehoram's crimes. He is plainly told that his sin should certainly ruin him. But no marvel that sinners are not frightened from sin, and to repentance, by the threatenings of misery in another world, when the certainty of misery in this world, the sinking of their estates, and the ruin of their health, will not restrain them from vicious courses. See Jehoram here stripped of all his comforts. Thus God plainly showed that the controversy was with him, and his house. He had slain all his brethren to strengthen himself; now, all his sons are slain but one. David's house must not be wholly destroyed, like those of Israel's kings, because a blessing was in it; that of the Messiah. Good men may be afflicted with diseases; but to them they are fatherly chastisements, and by the support of Divine consolations the soul may dwell at ease, even when the body lies in pain. To be sick and poor, sick and solitary, but especially to be sick and in sin, sick and under the curse of God, sick and without grace to bear it, is a most deplorable case. Wickedness and profaneness make men despicable, even in the eyes of those who have but little religion.